Membrane turnover and repair will be investigated in three biological systems - the toad urinary bladder, the erythrocyte, and normal and malignant cells grown in tissue culture. Particular emphasis will be placed on the effects of oxygen tension on membrane lipid synthesis and turnover, and the metabolic reponse of cells to oxygen and the toxic cellular metabolites produced. It is hoped that a better understanding of (1) the role of membrane turnover and repair in these systems, (2) the possible regulatory role of oxygen on this process, and (3) the cellular mechanisms for the detoxification of oxygen-induced deleterious metabolites will be derived from these studies.